‘Call in Jimmy Savile. You can’t afford to fuck about – bring in an expert. He may have fooled you, not fucking me.’ That was Jerry Sadowitz discussing the Cleveland child abuse scandal in his routine in 1987. A full 25 years before recent revelations, the New Jersey-born, Glasgow-raised and legendarily foul-mouthed comic and magician proved that he would always say what he thought, even if no one else was saying it, or even thinking it. Particularly if it enabled him to attack an institution or puncture a sense of moral complacency.

‘Offensive’ is an easy, maybe lazy, word to throw at Sadowitz. His is a broad church: race, religion, sexuality and disability come under scrutiny in his hate-filled, blistering, but also relentlessly funny shows. Gays, straights, blacks, whites, Christians, Jews, Muslims and often Sadowitz himself – all are strafed with F-words and C-bombs in performances that are unapologetically brutal, and often, as the Savile line suggests, uncomfortably close to the bone.

But despite being regularly cited as an inspiration by today’s legion of excoriating gag-merchants, he remains a cult figure, having never quite reached the audience he deserves, mainly because his act is deemed too controversial for television. These days, he performs occasionally, saying he ‘doesn’t get asked’ to do more shows. When we meet on the eve of his upcoming and potentially explosive West End run he’s wearing a Santa hat and doesn’t want to talk about his Savile comment (‘It doesn’t interest me’). At 51, he’s not in person as vein-poppingly angry as he comes across on stage, but he’s unlikely to be mistaken for a ray of sunshine. ‘I hate interviews,’ he says immediately and, indeed, he very rarely gives them. ‘You do what you do, you don’t describe what you do,’ he explains. ‘You do comedy; you don’t describe comedy. Well, Stewart Lee does. He makes a living out of it…’

A lot of contemporary comedians name you as an influence. How do you feel about that?‘I’m not pleased, because with most of them it’s not an influence, it is either the lines or the actual blocks of material. The subjects that I’ve talked about, I searched very deep to find those topics, and then had to find humour in them, simply because everything else had been done. Paedophilia had not been done, jokes about pensions had not been done, or necrophilia, or any of these subjects – they’re not nice subjects, but I wanted to find something original, rather than just go over well-trodden territory. But those subjects have been hijacked. Politically incorrect comedy is no genre: it’s me, and it’s been ripped off by loads and loads of comics. So, basically, when I say they’re all cunts, I’m not joking.’

So, many of the current generation of ‘politically incorrect’ comedians are…‘Bullshit? Yeah. They haven’t thought about it. They lifted a subject, which they’ve given no thought to, and they’ve made a flippant gag about it. I don’t think I’ve ever made a flippant gag in my life. It’s something that I’ve thought about, really hard about, and come up with something to say. It may be the absolute wrong thing to say, which is a legitimate part of comedy. I don’t always do the right thing. But however offensive it might sound, at least there’s a genuine thought.’

Last year saw your first proper UK tour in a 25-plus-year career. What took so long?‘People in the industry don’t want to come near me. Nobody can remember, and nobody knows, and nor is there any justification for why they wouldn’t work with me, but nobody wants to be the first one to do that. They would say I’m "difficult". Now, my interpretation of the word "difficult", as a comedian in this business, is somebody who demands a competent and honest promoter. In London, I’ve yet to see that combination.’

Isn’t that true for other comics?‘I imagine that a lot of comedians allow themselves to be abused because their talent is so lacking that anything they get, and anything they make, is a bonus to them. Or they are perhaps so upper middle class that they have enough money from mummy and daddy so they can afford to spend three or four years being ripped off by the industry. I can’t. This is my job, and I’ve got a very working-class ethic. I’m not proud of it, I’m not against it, but I do a job, and I’d quite like to get paid for the job, as agreed.’

Do you treat your material in the same way, working hard to make it a good show? ‘I put a ridiculous amount of care and attention into my shows because of my upbringing as a magician. I started magic when I was 11, and magic is always about great attention to detail. You can’t master 99 percent of a magic trick because if you don’t master the other 1 percent you’ll get caught: people will see how it’s done. I think I’ve brought that in to my performance and career, if you like. I want everything to be right. Otherwise the show isn’t good enough.’

Is that why the DVD you recorded last year hasn’t been released? You didn’t think the show was good enough? ‘Well, it was a number of reasons. First of all, I don’t like looking at myself: I don’t like myself, so I don’t really want to see anything of mine.’

But you don’t have to watch it… ‘No, I don’t. But that’s a problem. And the other problem is, I don’t want people looking at me on a DVD for the first time – and there are loads of people who haven’t seen me – and thinking: "Oh, he’s a bit like Frankie Boyle. Oh, he’s a bit like Ricky Gervais, he’s a bit like Jimmy Carr or Chubby Brown. I’ve heard Doug Stanhope do that…" So I don’t want people saying that about me.’

So that would rule out a TV show? ‘I’ve got a lot of ideas that I’d love to do for telly, but they’ll never see the light of day. Loads and loads of formats, and I think potentially very successful ones. But I don’t bother submitting them any more because television executives are just too stupid. They want film footage of it; you have to go away and make it, let them look at it, then they’re going to put it before an audience and see what they think of it, and all that really says is they haven’t got any judgment of their own. Funnily enough, I wrote a script and I saw myself in it, then later I thought: The person to play this would be Ricky Gervais. There you go!’

Do you want to make your audience uneasy, confront things they’d rather not? ‘I think you’re meant to leave your beliefs at the door. What’s that thing? “When you go and see a play, suspend your disbelief.” I think when you see a comedian you should suspend your beliefs. Anything that you hold dear, just put it at the door, leave it, and just take on board the material the person gives you from his perspective. You don’t have to agree with it, or believe in it. We could dissect each [gag], and the show could last about 12 hours. It’s the old cliché: comedy’s not meant to be analysed. Fuck, I hate talking about this. It’s all fucking dreadful.’ He stands up. ‘That’s enough to be getting on with, I think.’